Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent specifications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
As the quantity and speed of data communications over fiber optic systems rapidly increases due to the growing demand from Internet usage and other communications, improved all-optical switching systems are of increased interest to overcome the high cost and slow switching speeds of conventional switches. These conventional switches include, for example, various mechanical switches, electro-optic switches, and thermo-optic switches, such as, for example, described in U.S. Pat. Nos. 5,732,168 and 5,828,799, both to Donald. In particular, the increased complexity and cost of switching systems which involve switching from an optical signal to an electrical signal and then back to an optical signal have increased the level of interest in improved all-optical switches.
An all-optical switch provides switching of an optical signal from one input path to a selected one of a plurality of different output paths without any intermediate conversion of the optical signal to an electrical signal. This is typically accomplished by applying an electrical signal to a switchable element to cause the optical signal to be selectively switched. These electro-optic switches are responsive to the electrical signal to selectively switch the light of the optical signal from the input path to the selected one of the output paths.
A variety of approaches are known for making all-optical or hybrid optical switches, such as, for example, described in U.S. Pat. No. 5,905,587 to Maeno, et al.; U.S. Pat. No. 5,923,798 to Aksyuk, et al.; U.S. Pat. No. 5,970,185 to Baker, et al.; U.S. Pat. No. 5,841,912 to Mueller-Fiedler, et al.; U.S. Pat. No. 5,091,984 to Kobayashi, et al.; U.S. Pat. No. 5,406,407 to Wolff; U.S. Pat. No. 5,740,287 to Scalora, et al.; U.S. Pat. No. 5,960,133 to Tomlinson; U.S. Pat. No. 5,539,100 to Wasielewski et al.; and U.S. Pat. No. 5,943,453 to Hodgson.
A variety of approaches are also known for making electro-optic modulators; as illustrated, for example, by U.S. Pat. No. 5,528,414 to Oakley, U.S. Pat. No. 5,550,670 to Zielinski, et al.; U.S. Pat. No. 5,566,257 to Jaeger, et al.; U.S. Pat. No. 5,825,525 to Harwit; 6,172,791 to Gill, et al.; U.S. Pat. No. 6,204,951 to Coward, et al.; and U.S. Pat. No. 6,222,666 to Moulin.
The need for improved optical switches is increased by the use of wavelength multiplexing which converts the optical signal in the optical fiber into, for example, 16 signals at 16 different wavelengths in a near-infrared range of about 1540 to 1560 nm, as, for example, described in Bell Labs Technical Journal, January-March 1999, pages 207 to 229, and references therein, by Giles et al.; and in U.S. Pat. No. 5,959,749 to Danagher et al. The primary function of the optical switch is to add and/or drop optical signals from the multiple wavelengths traveling through the optical fiber. It would be highly desirable to have arrays of optical switches to handle the optical signals from multiple wavelengths per optical fiber and from multiple optical fibers, such as up to 100×100 or greater optical switch arrays. Also, it would be highly desirable if the response time for the optical switch is ultrafast, such as 1 nanosecond or less.
As the speed of data communications over fiber optic systems increases beyond 2.5 gigabits per second (Gbps) to 10 Gbps and higher, the modulation of the laser signal sources to produce the optical signal for transmission typically changes from direct “on-off” modulation of the laser to an external or integrated “hybrid” modulator for the laser in order to provide the required quality for the optical signal. These optical modulators include interferometric phase modulators, such as lithium niobate and electro-optic polymer modulators, and electro-absorption modulators, such as indium phosphide (InP) modulators, as known in the art of electro-optic modulators.
It would be advantageous if an all-optical switching system were available which avoided the complexity and cost of optical-electrical-optical (so-called O-E-O) switching systems, conventional electro-optic and other all-optical switching systems while increasing the speed of the optical signal switching times from the millisecond range to the nanosecond or picosecond ranges. It would be further advantageous if an all-optical switching system were available which could be utilized for ultrafast optical modulators in fiber optic and other optical transmission systems to provide greater optical signal quality, smaller sizes capable of monolithic integration with the lasers and other optical components, lower energy requirements, higher signal transmission speeds, and lower costs.